14? ?? ??? ? ??? ?? ???????, ? ???? ?????? ???? ??? ????? ?? 696? ????? ??, ??? ? 4626?? ??? ????.

?? ? ??? ??? ??? 0.12ppm ??? ? ‘???’, 0.3ppm ???? ‘??’, 0.5ppm ???? ‘????’? ?? ????.

???? ???? ??? ??? ???, ??? ?? ????? ???? ??. ? ??? ???? ?????? ????? ???? ???? ??? ????? ??? ??.

????? ???? ???? ??? ???? ???? ?? ????? ????.

?? ??? ?? ????? 2000? 0.017ppm, 2001? 0.015ppm, 2002? 0.014ppm???? ?????? ??? ??? 2000? 8?, 2001? 4?, 2002? 1????.

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